Y'all (/jɔːl/yawl) is a contraction of the words "you" and "all". It is used as a plural second-person pronoun.

Formally, you would use the word "you" or the words "you all" when referring to a group of people in the second person and "they" when referring to a group of people in the third person.

Informally, in the second person, "you guys," "y'all," etc. is fine.

Your confusion may that we use the word "you" in both the singular and plural in the second person.

So, formally:"Where are you going?""Where are you all going?"

Informally:"Where are you guys going?""Where are all you all going?"

Or any way you want as long as the party you're speaking to understands what you're saying. That's what informal English is about.

So in correct formal English, "You all" is really the correct phrase. The South has it right! In addition, the term "guy" is informally defined as a "young man", as we all would understand the term of "guys and dolls" as meaning the gender of male and female. So the use of "you guys" is really, formally incorrect in both grammar and gender identification, but the phrase has become a regional colloquialism, that has wide usage, and is the norm in many areas of the country.

Again, there's nothing wrong with you-all or y'all, but it's a regionalism that will peg you as being from the southern United States if you use it because today, in standard English the word you is both the singular and plural second-person nominative pronoun—that just means you use it when you're talking to one person or a group of people. But a long time ago English actually had different singular and plural second-person pronouns. Thou was singular and ye (y-e) was plural.